Study On The Reduction Of Benzaldehyde And Acetophenone By Calcium-Alginate-Immobilized Baker's Yeast In Organic Solvent

Recently, catalysis by the whole cells in organic solvent has attracted attention of more and more researchers and has become a new hotspot in the field of biotechnology.In this thesis, the reduction ability of benzaldehyde by baker's yeast and another 8 strains of yeast in water and in organic solvent was studied, the effects of medium constitute, cultivation time, sodium alginate concentration, pH, organic solvent, co-substrate, initial concentration of substrate, rev of orbital shake and temperature on the reduction by Calcium-Alginate-immobilized baker's yeast in organic solvent were studied, and the reuse of Calcium-Alginate-immobilized baker's yeast with 6 and 24 hours as a period was tested. The substrate of all the above studies is benzaldehyde.Except for Cancida 2". cultivated baker's yeast and another 7 strains of yeast all can reduce benzaldehyde to benzyl alcohol in water and in organic solvent.When baker's yeast cultivated in YPD medium for 1 or 4 days, the ability of reduction of baker's yeast is highest. Baker's yeast without precultivation also has the ability of reduction. Product concentration would be increased with increase of quantity of cells, and product concentration increase more quickly when quantity of yeast is little.Sodium alginate solution whose concentration is within 1-5% can be used to immobilize baker's yeast, and the immobilized baker's yeast made in alginate concentration of 3% had higher ability of reduction than that in otherconcentration. When pH of the buffer used to dissolve yeast is 10, the highest product concentration could be obtained.Organic solvent would affect on the ability of reduction by immobilized baker's yeast. In general, the higher LogP of solvent is, the higher the ability of reduction the yeast has. Within the so-substrate studied, a majority of alcohols could not increase the concentration of product. Only with higher alcohols as co-substrate in hexane, it could get higher product concentration.When the initial substrate concentration increase from 660 mM to 990 mM, the substrate concentration within bead varies from 41.2 mM to 84.3 mM. With the increase of substrate concentration, the product concentration in solvent and within bead all decrease greatly.The product concentration increases almost linearly with rev of orbital shake increasing. The optimum temperature is 35℃ when solvent is hexane and 30℃ when solvent is butylacetate.The immobilized yeast could be reused for 2 times with 24 hours as a culture period and for more than 6 times with 6 hours as a culture period.When the substrate is acetophenon, the effect of concentration of alginate. sorts of organic solvent, sorts of co-substrate and initial concentration of substrate on the reduction of Calcium-Alginate-immobilized baker's yeast in organic solvent is similar to the results as the substrate was benzaldehy. But the best pH is pH 4 and pH 10, perhaps because the enzymes participate in the reduction of benzaldehyde and acetophenon are slightly different.